The purpose of this project is to determine the effects of sugar substitutes of a low cariogenic potential on the growth, acid production and polysaccharide synthesis by oral bacteria. We reported that the sucrose derivatives, palatinose and palatinit did not support growth or acid formation by several different species of oral streptococci and that these compounds inhibited glucan formation by S. mutans. To determine if human saliva could convert these derivatives to fermentable substrates we carried out growth experiments with strains of S. mutans and S. sanguis in media containing the sucrose derivatives, low levels of sucrose and (plus and minus) clarified human saliva. The results showed that the derivatives in the presence of saliva had little, if any, influence on growth, acid formation or adherence of the bacteria. Under the conditions of the study the sucrose derivatives were not converted to fermentable carbohydrate by human saliva. Xylitol inhibited the growth and acid production by strains of S. mutans, S. sanguis, S. mitior and A. viscosus. 14C-xylitol was taken up by both growing and resting cells of S. mutans, S. sanguis and S. mitior. The major radioactive metabolite extracted from S. mitior cells was xylitol-5-phosphate. The results suggest that the intracellular accumulation of xylitol-5-phosphate is related to the observed inhibition of bacterial growth.